Temporomandibular joint implants and methods of treating a temporomandibular joint

ABSTRACT

The present disclosure provides intramedullary mandibular implants for the temporomandibular joint. The mandibular implants include a stem portion, a collar portion and a head portion. The stem, collar and head portions may be integral. The stem portion may define an inferior end and the head portion may define a superior end of the implants. The head portion may be arcuate in the sagittal plane to provide an articulating surface with a fossa or a fossa component. The collar portion may be intermediate of the head and stem portions and form a channel between an interior surface of the collar portion and an exterior surface of the stem portion. In use, the stem portion may be implanted within a condyle of a mandible such that an end portion of the condyle is situated within the channel of the implant and the head portion articulates with the fossa or fossa component.

CROSS REFERENCE

This Application is a continuation of PCT Application No.PCT/US2015/038952 filed on Jul. 2, 2015, which claimed the benefit ofpriority from U.S. Provisional Application No. 62/020,103 filed on Jul.2, 2014, all of which are incorporated herein by reference.

BACKGROUND

The present disclosure generally relates to implants for, and methodsrelating to, temporomandibular disorders.

One aspect of the craniomandibular system is that the temporomandibularjoint (TMJ) moves in synchrony with its contralateral part. Therotational and translational movements of the TMJ are supported by anintra articular disc. TMJ is thereby a bilateral synovial articulationbetween the condyle (rounded prominence) at the end of the mandible andthe fossa (a concave depression) in the squamous portion of the temporalbone. The name of the joint is derived from the two bones which form thejoint: the upper temporal bone which is part of the cranium, and thelower jawbone or mandible. The functions performed by this joint(chewing, swallowing, speaking, aesthetics, etc.) are performed with theassociation of several structures, such as masticatory muscles,craniomandibular ligaments, and nervous connections derived from V andVII cranial nerves. TMJ has three degrees of motion, which are activatedwhile eating, talking, breathing, and even when changing horizontal orvertical position, producing an almost continuous functional demand onthe TMJ. The volume of movement of the TMJ increases the likelyhood ofpathological disorders. The effects on the TMJ due to pathologicaldisorders usually are not apparent until later in the disease process.While RA may be the most frequent articular degenerative process of theTMJ, other articular degenerative processes can affect the TMJ, such aspsoriac arthritis, systemic lupus, erythematous, gout, non-inflammatorydiseases, ailments, trauma, muscle disorders, and the like. Articulardegeneration of the TMJ typically leads to severe damage of the TMJ andpain. Patients may experience symptoms including deep and dullpreauricular pain, headaches, myofascial pains, morning jaw stiffness,clicking, decreased bite form, difficulty in swallowing and showing,decreased jaw mobility and occlusal changes. In some scenarios, thecondyle may erode, such as flatten, lose height, and/or lose volume.Further, the intra-articular pannus surrounding the articular disk mayform and lead to destruction of the disk, condylar resorption anderosion of the fossa.

Degenerative disorders of the TMJ has typically been treated withanti-inflammatory drugs. However, once the temporomandibular joint hasbeen compromised, surgical treatment is commonly a preferred or moreeffective option. TMJ implants have increased in demand as the amount ofjaw joint and muscle disorders causing articular degenerative haveincreased. Current typical TMJ implants for articular degeneration faceseveral deficiencies in both design and long-term performance. Forexample, evidence suggests that many of the failures of typical TMJimplants are related to defects in design and materials, rather thanmaterial fatigue as TMJ forces are relatively low (e.g., less than about450 MPa) when compared to the strength of common implant materials(e.g., titanium or Cr-Co-Mo alloys).

Current TMJ implants or treatment devices typically mimic the “ball andsocket” design of prosthetic hip implants. Specifically, current TMJimplants may consist of three components: a condylar or mandibularimplant made of metal, a fossa implant made of metal or a hard plasticpolyethylene, and metal screws that attach the condylar and fossaimplants to the exterior surface of their corresponding bones. Manymandibular component designs are relatively similar in that they providea plate portion for fixation to the mandible, and an articulationsurface for abutment with the fossa component. The plate portion of themandibular component is typically attached to the exterior of themandible (i.e., lateral installation), such as against the outer lateralsurface of the condyle with screws passing through fixation apertures ofthe plate portion.

Rotation and/or translation of the mandible with respect to the fossa(and therefore the corresponding components of current TMJ implants) isprimarily provided by four muscles: the masseter, the medial pterigoid,the temporalis (activate for mouth closing), and the lateral pterygoid(activate for mouth opening). Each of the muscles apply different forceson the TMJ—and therefore to the fossa and mandibular components oftypical TMJ implants. Analysis has shown that current TMJ implantscannot adequately or properly manage mechanical forces applied theretoby a patient's muscles. For example, current mandibular components andcorresponding fixation screws of TMJ implants may not adequately addressthe stress distribution of the component.

Loads transmitted inferiorly to the top of typical mandibular componentsare transmitted from the mandibular component to the mandible throughthe screws fixing the mandibular component to the mandible. The firstscrew of the mandibular component in the superior-to-inferior directionis subject to the maximum stress. For example, the high von Mises stressof current mandibular components may vary between 106 and 126 MPa, andhighest stress may be positioned adjacent to first screw. Common priorimplants claim to compensate for the high stresses on the first screw bydistributing the load over other screws. Regardless, however, thefixation screws of current TMJ implants transmit loads from the implantto the mandible bone and are the points where the maximum von Misesstresses are found. These high stresses on the fixation screws,especially on the first screw, fixing the mandibular component to themandible commonly lead to failures of such current TMJ implants.Further, lateral installation of such exteriorly mounted mandibularcomponents of current TMJ implants fails to provide functional ranges ofmotion of the joint that are similar to “normal” physiologicalparameters.

As a result, considering the state of the art that exists today, thereis a need for better implants and methods for TMJ treatment thatadequately support the stresses and loads of the temporomandibular jointto provide reliable, long-lasting treatment solutions that also allowfor more functional ranges of motion.

SUMMARY OF THE INVENTION

In one aspect, the present disclosure provides for a mandibular implant.The mandibular implant includes an intramedullary stem portion, a collarportion, and a head portion. The collar portion extends substantiallyabout the stem portion, and forms a channel between the collar portionand the stem portion. The head portion includes an arcuate externalsurface. The collar portion is intermediate the stem portion and thehead portion. The stem portion, the collar portion and the head portionbeing substantially aligned.

In another aspect, the present disclosure provides for a system forreplacing a temporomandibular joint. The system includes a biocompatiblefossa component, a biocompatible mandibular component, an intramedullarystem portion, a collar portion, and a head portion. The biocompatiblefossa component is configured to be fixed to a temporal bone. Thebiocompatible mandibular component is configured to be fixed to amandible bone. The collar portion extends substantially about the stemportion, and the collar portion forms a channel between the collarportion and the stem portion. The head portion includes an arcuateexternal surface. The collar portion is intermediate the stem portionand the head portion.

In another aspect, the present disclosure provides for a method oftreating a temporomandibular joint. The method includes forming anaperture in a condyle of a mandible. The method also includes insertinga stem portion of a mandibular implant into the aperture in the condyle.The method further includes implanting the mandibular implant in theaperture of the condyle such that an end portion of the condyle ispositioned within a channel formed between the stem portion and a collarportion of the mandibular implant, and a head portion including anarcuate external surface of the mandibular implant is positionedsuperior to the condyle.

In another aspect, the present disclosure provides a mandibular implantincluding an intramedullary stem portion, a collar portion and a headportion. The collar portion extends substantially about the stemportion, and forma a channel extending between the collar portion andthe stem portion about the stem portion. The head portion includes anarcuate external surface. The collar portion is intermediate the stemportion and the head portion, and the stem portion, the collar portionand the head portion are substantially aligned.

In some embodiments, the stem portion, the collar portion and the headportion are integral to each other. In some embodiments, the stemportion is configured to be implanted within a condyle of a mandible. Insome embodiments, the stem portion defines a free end and is elongatebetween the inferior end and a superior end portion. In some suchembodiments, the collar portion extends from the superior end portion ofthe stem portion.

In some embodiments, the collar portion includes a first portion with anouter surface that tapers outwardly as it extends in a first directionfrom the head portion towards the stem portion. In some suchembodiments, the collar portion includes a second portion that extendsfrom the first portion along the first direction and about the stemportion. In some such embodiments, at least the second portion of thecollar portion forms the channel. In some other such embodiments, thesecond portion of the collar portion is ring-shaped, and wherein thestem portion is cylindrical.

In some embodiments, the stem portion defines a first axis and thecollar portion defines a second axis, and wherein the first axis and thesecond axis are aligned. In some such embodiments, the head portiondefines a third axis that is oriented substantially perpendicular to thefirst axis and the second axis, and wherein the head portion extendsalong the direction of the third axis. In some such embodiments, thearcuate external surface of the head portion extends about the thirdaxis. In some other such embodiments, the arcuate external surface ofthe head portion extends linearly along the direction of the third axis.

In some embodiments, the stem portion and the collar portion define afirst axis and the head portion defines a third axis orientedsubstantially perpendicular to the first axis, and wherein the stemportion defines a first width extending along the direction of the thirdaxis within the range of about 2 mm to about 9 mm, the channel defines asecond width extending along the direction of the third axis and aboutthe stem portion of about 2 mm, and the head portion defines a thirdwidth extending along the direction of the third axis within the rangeof about 10 mm to about 15 mm. In some embodiments, the channel definesa width extending between an outer surface of the stem portion and aninner surface of the collar portion of about 2 mm and a length extendingsubstantially perpendicular to the width of about 4 mm.

In another aspect, the present disclosure provides a system forreplacing a temporomandibular joint. The system includes a biocompatiblefossa component configured to be fixed to a temporal bone and abiocompatible mandibular component configured to be fixed to a mandiblebone. The mandibular component includes an intramedullary stem portion,a collar portion and a head portion. The collar portion extendssubstantially about the stem portion, and forms a channel between thecollar portion and the stem portion. The head portion includes a firstarcuate external surface. The collar portion is intermediate the stemportion and the head portion.

In some embodiments, the biocompatible fossa includes a second arcuatesurface configured to abut and articulate with the first arcuateexternal surface of the head portion. In some such embodiments, thefirst arcuate external surface of the head portion is defined by a firstradius, and the second arcuate surface of the biocompatible fossa isdefined by a second radius that is greater than the first radius. Insome embodiments, the stem portion, the collar portion and the headportion are of one-piece construction.

In some embodiments, the collar portion includes a first portion with aouter surface that tapers outwardly as it extends in a first directionfrom the head portion towards the stem portion. In some suchembodiments, the collar portion includes a second portion that extendsfrom the first portion along the first direction and about the stemportion. In some such embodiments, at least the second portion of thecollar portion forms the channel about the stem portion.

In some embodiments, the stem portion defines a first axis and thecollar portion defines a second axis aligned with the first axis, thehead portion defines a third axis that is oriented substantiallyperpendicular to the first axis and the second axis, and the headportion is elongated along the direction of the third axis. In some suchembodiments, the arcuate external surface of the head portion extends atleast partially about the third axis and extends linearly along thedirection of the third axis for a first width.

In another aspect, the present disclosure provides a method of treatinga temporomandibular joint. The method includes forming an aperture in acondyle of a mandible. The method further includes aligning a stemportion of a mandibular implant with the aperture in the condyle. Themethod further includes implanting the mandibular implant into theaperture of the condyle such that an end portion of the condyleextending about the stem portion is positioned within a channel of themandibular implant formed between the stem portion and a collar portionof the implant, and such that a head portion of the implant including anarcuate external surface is positioned superior to the condyle forarticulation with a fossa or fossa component.

In some embodiments, the collar portion of the implant forms a ferruleeffect to the end portion of the condyle. In some embodiments, themethod further includes resecting a superior tip portion of the condyleof the mandible. In some embodiments, the method further includesimplanting the mandibular implant into the aperture of the condyle suchthat the implant is angled in the anterior-to-posterior direction as itextends into the condyle in the superior-to-inferior direction. In somesuch embodiments, the method further includes implanting the mandibularimplant into the aperture of the condyle such that the implant issubstantially parallel to the sagittal plane. In some other suchembodiments, the method further includes implanting the mandibularimplant into the aperture of the condyle such that the implant is angledin the lateral-to-medial direction as is extends into the condyle in thesuperior-to-inferior direction.

In some such embodiments, the method further includes implanting a fossacomponent in a temporal bone corresponding to the condyle of themandible. In some such embodiments, the arcuate external surface of thehead portion of the implant is elongated and extends linearly along afirst width, and the method further includes orienting the implant suchthat the first width of the head portion extends in the medial-lateraldirection.

These and other objects, features and advantages of this disclosure willbecome apparent from the following detailed description of the variousaspects of the disclosure taken in conjunction with the accompanyingdrawings.

DRAWINGS

FIG. 1 is a superior perspective view of an exemplary intramedullarymandibular TMJ implant according to the present disclosure;

FIG. 2 is an inferior perspective view of the TMJ implant of FIG. 1;

FIG. 3 is a posterior view of the TMJ implant of FIG. 1;

FIG. 4 is a lateral view of the TMJ implant of FIG. 1;

FIG. 5 is a superior view of the TMJ implant of FIG. 1;

FIG. 6 is an inferior view of the TMJ implant of FIG. 1;

FIG. 7 is an posterior cross-sectional view of the TMJ implant of FIG.1;

FIG. 8 is a lateral view of the TMJ implant of FIG. 1 implanted in acondyle of a mandible;

FIG. 9 is the lateral view of FIG. 8 illustrating an intramedullary stemof the implant, and a portion of the condyle positioned within a channelof the implant;

FIG. 10 is an anterior view of the implanted TMJ implant of FIG. 8; and

FIG. 11 is a lateral view of the implanted TMJ implant of FIG. 8engaging a fossa or fossa component of a corresponding temporal bone.

DETAILED DESCRIPTION

Each embodiment presented below facilitates the explanation of certainaspects of the disclosure, and should not be interpreted as limiting thescope of the disclosure. Moreover, approximating language, as usedherein throughout the specification and claims, may be applied to modifyany quantitative representation that could permissibly vary withoutresulting in a change in the basic function to which it is related.Accordingly, a value modified by a term or terms, such as “about,” isnot limited to the precise value specified. In some instances, theapproximating language may correspond to the precision of an instrumentfor measuring the value. When introducing elements of variousembodiments, the articles “a,” “an,” “the,” and “said” are intended tomean that there are one or more of the elements. The terms “comprising,”“including,” and “having” are intended to be inclusive and mean thatthere may be additional elements other than the listed elements. As usedherein, the terms “may” and “may be” indicate a possibility of anoccurrence within a set of circumstances; a possession of a specifiedproperty, characteristic or function; and/or qualify another verb byexpressing one or more of an ability, capability, or possibilityassociated with the qualified verb. Accordingly, usage of “may” and “maybe” indicates that a modified term is apparently appropriate, capable,or suitable for an indicated capacity, function, or usage, while takinginto account that in some circumstances, the modified term may sometimesnot be appropriate, capable, or suitable. Any examples of operatingparameters are not exclusive of other parameters of the disclosedembodiments. Components, aspects, features, configurations,arrangements, uses and the like described, illustrated or otherwisedisclosed herein with respect to any particular embodiment may similarlybe applied to any other embodiment disclosed herein.

In this application, including the claims, the terms proximal, distal,anterior, posterior, medial, lateral, superior, inferior, cranial andcaudal are defined by their standard usage for indicating a particularaspect or orientation of a bone, other anatomy, implant, device or thelike according to the relative disposition of the natural anatomy ordirectional terms of reference with respect thereto, as is known byordinary skill in the art. For example, “proximal” means the portion ofan implant or anatomy nearest a relative aspect, while “distal”indicates the portion of the implant or anatomy farthest from a relativeaspect. As for directional terms, “anterior” is a direction towards thefront side of the body, “posterior” means a direction towards the backside of the body, “medial” means towards the midline of the body,“lateral” is a direction towards the sides or away from the midline ofthe body, “superior” means a direction above and “inferior” means adirection below another aspect.

The present disclosure provides apparatuses, devices, systems,components and related methods of use which may facilitate motion of,and/or provide structural support to, the temporomandibular joint(hereinafter the “TMJ”) via an implant. In some embodiments, theimplants of the present disclosure may include an intramedullarycomponent that is particularly advantageous for use with the mandible(i.e., a mandibular component or implant), such as with each condyleportion of the mandible. In some embodiments, the apparatus, devices,systems, components and related methods of use may include anintramedullary mandibular component and a fossa component that is fixedto the temporal bone at or about the fossa thereof. The fossa componentmay be configured such that a portion of the intramedullary mandibularcomponent articulates on, or with, the fossa component, as describedfurther below.

As shown in FIGS. 1-11, the present disclosure provides an exemplarymandibular implant or component 10 that is configured as anintramedullary component. The mandibular implant 10 is particularlyconfigured to be situated within a condyle of the mandible, as shown inFIGS. 8-11. As shown in FIGS. 1-11, the mandibular implant 10 includesan exemplary stem portion 12, an exemplary collar portion 14, and anexemplary head portion 16. The stem portion 12, collar portion 14, andhead portion 16 may be integral to each other or of one-piececonstruction. In some alternative embodiments, at least one of the stemportion 12, collar portion 14, and head portion 16 may be a separate anddistinct component that is fixed to at least one another component, andthereby the component may be interchangeable.

The mandibular implant 10 (e.g., the stem portion 12, collar portion 14,and head portion 16) may be made from a biologically or physiologicallycompatible material. In some such embodiments, the mandibular component10 (e.g., the stem portion 12, collar portion 14, and head portion 16)may be metal, carbon fiber, polymer of suitable stiffness, orcombinations thereof In some embodiments, the mandibular implant 10 maybe titanium or a titanium alloy (e.g., Ti-6LV). The mandibular component10, at least in part, may include or be formed of a material that isradiolucent. In some embodiments, the stem portion 12, collar portion14, and head portion 16 may be made of substantially the same material(e.g., titanium or a titanium alloy).

The stem portion 12 of the mandibular implant 10 may allow the implant10 to be situated within the mandible (i.e., intramedullary). Theintramedullary stem portion 12 may be elongated and otherwise sizedand/or shaped to fit within the mandible, such as into a condyle of themandible extending at least generally in the superior-inferiordirection. For example, as shown in the illustrated exemplaryembodiment, the stem portion 12 may be elongate and cylindrical, suchthat the stem portion 12 extends substantially linearly and includes asubstantially consistent shape along the length of the stem portion 12.In some alternative embodiments, the stem portion 12 may be tapered. Asshown in FIGS. 1, 2 and 5-7, the stem portion 12 may define an axis X-X.The stem portion 12 may define a circular cross-section in a planeextending perpendicular to the axis X-X (i.e., form the axis X-X). Inalternative embodiments, the stem portion 12 may not be cylindrical, butmay include another cross-sectional shape in a plane extendingperpendicular to the axis X-X. For example, the stem portion 12 mayinclude an elliptical or oval cross-section. In some other embodiments,the stem portion 12 may include fins, ridges or other anti-rotationmembers. Such non-circular cross-sections and/or anti-rotation membersmay act to substantially prevent or limit rotation of the intramedullarystem portion 12 after implantation.

The exterior surface 13 of the stem portion 12 may be substantiallysmooth and arcuate, as shown in FIGS. 1-5. In some embodiments, theexterior surface 13 of the stem portion 12 may include a surface textureor material that aids in bone growth about, within or coupled to thestem portion 12 to assist in anchoring the stem portion within themandible.

The stem portion 12 may include or define an inferior end 18 thatdefines the inferior end of the mandibular implant 10, as shown in FIGS.1-4, 6, 7 and 9. The stem portion 12 may be tapered or otherwise reducein cross-sectional area as it approaches the inferior end 18. A taperedinferior end 18 of the stem portion 12 may assist in inserting the stemportion 12, and thereby the mandibular implant 10 itself, into anaperture or passageway in a condyle of the mandible (i.e., the stemportion 12 may be configured to be an intramedullary stem portion 12).In some alternative embodiments, the inferior end 18 of the stem portion12 may not be tapered.

As shown in the cross-sectional view of FIG. 7, the stem portion 12 maydefine a length L1 (e.g., a length along the inferior-superior directionor along the axis X-X). The length L1 of the stem portion 12 may beparticularly suited for use with a mandible, such as being implantedwithin a condyle of the mandible generally in the inferior-superiordirection. In some such embodiments, the length L1 of the stem portion12 may be within the range of about 30 mm to about 10 mm, or within therange of about 25 mm to about 15 mm. In the illustrated exemplaryembodiment of FIGS. 1-11, the length L1 of the stem portion 12 is about20 mm.

As also shown in the cross-sectional view of FIG. 7, the stem portion 12of the mandibular implant 10 may define a width W1 (e.g., a width alongthe transverse plane). The width W1 of the stem portion 12 (and/or thewidth of other portions of the implant 10) may extend in a directionthat extends substantially perpendicular to the axis X-X. In embodimentsthat include a cylindrical stem portion 12, the width W1 may correspondto the diameter of the stem portion 12, and one half of the width W1 maycorrespond to the radius of the arcuate exterior surface 13 of the stemportion 12. The width W1 of the stem portion 12 may be particularlysuited for use with a mandible, such as being implanted within a condyleof the mandible. In some such embodiments, the width W1 of the stemportion 12 may be within the range of about 2 mm to about 12 mm, orwithin the range of about 2 mm to about 9 mm, or within the range ofabout 5 mm to about 9 mm. In the illustrated exemplary embodiment ofFIGS. 1-11, the width W1 of the stem portion 12 is about 7 mm.

With reference to FIGS. 1-11, the collar or ferrule ring portion 14 ofthe of the mandibular implant 10 may be provided at an end portion 20 ofthe stem portion 12 that substantially opposes the inferior end 18thereof, such as a superior end portion 20 of the stem portion 12 (asshown in the cross-sectional view of FIG. 7). As discussed above, thecollar portion 14 may be integral with, or fixed to, the superior endportion 20 of the stem portion 12. The collar portion 14 may be providedor extend substantially about the stem portion 12 (e.g., about thecircumference of the stem portion 12), such as substantially about theaxis X-X of the stem portion 12. In some embodiments, the collar portion14 may define an axis that is substantially aligned with the axis X-X ofthe stem portion 12. As such, the axis X-X may correspond to an axis ofboth the stem portion 12 and the collar portion 14.

As shown in FIGS. 1-11, the collar or ferrule portion 14 may extend awayfrom the superior end portion 20 of the stem portion 12, such as alongthe axis X-X and/or along a direction angled with respect to the axisX-X. For example, the collar portion 14 may extend away from theexterior surface 13 of the stem portion 12 (e.g., generally in thetransverse plane) and extend toward the inferior end 18 of the stemportion 12 (e.g., generally inferiorly). In this way, the collar portion14 may form a channel, space, cavity or void 22 between an interiorsurface 24 of the collar portion 14 and an adjacent portion of theexterior surface 13 of the superior portion 20 of the stem portion 12(i.e., the channel 22 may be provided about the axis X-X). The channel22 between the collar portion 14 and the stem portion 12 may therebyextend in the transverse plane and along the superior-inferiordirection. The collar portion 14 may be configured to accept acorresponding band or ring of bone within the channel 22, such as acorresponding portion of a condyle as explained further below. Forexample, as shown in the cross-sectional view of FIG. 7, the channel 22may define a width W2 (e.g., a width along the transverse plane) of atleast about 2 mm about the stem portion 12 to accept at least about 2 mmof a condyle bone therein.

In the exemplary embodiment shown in FIGS. 1-11, the collar or ferruleportion 14 of the mandibular implant 10 includes a first portion 26 thatis substantially tapered. The exterior surface of the first portion 26may be substantially conical in shape such that it progressively tapersor extends away from the exterior surface 13 of the stem portion 12 asit extends in a superior-to-inferior direction (e.g., along the axisX-X). Stated differently, the first portion 26 of the collar portion 14may extend angularly away from the exterior surface 13 of the superiorend portion 20 of the stem portion 12 as it extends therefrom towardsthe inferior end 18 of the stem portion 12. In the exemplary illustratedembodiment, the first portion 26 extends angularly away from theexterior surface 13 of the superior end portion 20 of the stem portion12 at an angle of about 40 degrees as it extends towards the inferiorend 18 to facilitate load transfer and proper seating of the implant 10during use.

The exterior surface and/or an interior surface of the first portion 26of the collar portion 14 may be conical in shape. In the exemplaryembodiment, the first portion 26 is not spaced from the stem portion 12,but rather substantially solidly extends from the superior end portion20 of the stem portion 12. In this way, the first portion 26 may notform at least a portion of the channel 22 other than, for example, asuperior end 27 of the channel 22. However, in alternative embodiments,the first portion 26 may define an inner surface that is spaced from thestem portion 12, and thereby at least partially form the channel 22. Thetapered (e.g., conical) shaped first portion 26 of the collar portion 14may be centered about the stem portion 12, e.g., aligned with the axisX-X. For example, the first portion 26 of the collar portion 14 maydefine an axis that is aligned with the axis X-X.

As also shown in FIGS. 1-11, the exemplary collar or ferrule portion 14of the mandibular implant 10 includes a second portion 28 that mayextend from the first portion 26 and be spaced, at least in part, fromthe outer surface 13 of the stem portion 12. In this way, the secondportion 28 may include or define an inner surface 24 that is adjacentand spaced from the outer surface 13 of the stem portion 12, therebyforming the channel 22 therebetween. The second portion 28 may extendfrom the first portion 26 of the collar portion 14 substantially in thesuperior-to-inferior direction. In some embodiments, the second portion28 of the collar portion 14 may be substantially ring shaped (i.e.,cylindrical and hollow). The exterior surface and/or interior surface ofthe second portion 28 of the collar portion 14 may be cylindrical. Insome embodiments, the second portion 28 of the collar portion 14 may becentered about the stem portion 12, e.g., aligned with the axis X-X. Forexample, the second portion 28 of the collar portion 14 may define anaxis that is aligned with the axis X-X of the stem portion 12 (andpotentially also aligned with the axis of first portion 26). In thisway, the inner surface 24 of the second portion 28 of the collar portion14 may form a ring-shaped channel 22 (i.e., a hollow band) between thestem portion 12 and the second portion 12. The channel 22 may facilitatebone contact and/or load transfer during use, such as use with a condyleof a mandible. In other embodiments, the channel 22 may not be ringshaped, but may define or include an oval or other non-circular shape.

In some embodiments, the channel 22 (e.g., a ring or hollow cylindricalshaped channel 22) formed between the second portion 28 of the collarportion 14 and the superior aspect of the stem portion 12 may define awidth W2 and a length L2. The width W2 may be a width along thetransverse plane (e.g., along the axis X-X), and the length L2 may be alength in the superior-inferior direction (and/or perpendicular to theaxis X-X). In the exemplary illustrated embodiment of FIGS. 1-11, thewidth W2 of the channel 22 is about 2 mm, and the length L2 of thechannel 22 is about 4 mm. Such dimensions may be particularly wellsuited for acceptance of a tip portion of a condyle within the channel22 to facilitate bone support and load transfer.

It is noted that the collar or ferrule portion 14 may be shapeddifferently, or include differing first and second portions 26, 28, thanas depicted in FIGS. 1-11 to accommodate different sized and/or shapedanatomical structure. For example, the entirety of the collar or ferruleportion 14 may be conical in shape, and/or the channel 22 may be taperedand/or conical in shape (as opposed to cylindrical). The collar portion14 may define any shape or configuration such that the collar portion 14forms a space or channel 22 between the collar portion 14 and the stemportion 12 that extends both in the transverse plane and theinferior-superior direction, and that extends substantially about thestem portion 12 (e.g., about the axis X-X). Stated differently, thecollar portion 14 may define any shape or configuration such that thecollar portion 14 forms a space or channel 22 between the collar portion14 and the stem portion 12 that is configured to accept the tip portionof a condyle of a mandible within the channel 22. As explained furtherbelow, the collar portion 14 may distribute or share forces occurringduring use of the temporomandibular joint to the implant 10 (e.g.,inside the implant) as opposed to the condyle, and may improve overallforce stresses or loads resulting from mastication and normal jawfunctions. The collar portion 14 may also prevent the condyle fromsplitting or splintering from the intramedullary stem portion 12extending within the condyle.

As shown in FIGS. 1-11, the mandibular implant 10 may include a headportion 16 that is positioned at the superior end or portion of thecollar portion 14. As discussed above, the head portion 16 may beintegral with the collar portion 14 and/or the stem portion 12, or fixedto the collar portion 14 and/or the stem portion 12. The head portion 16may define an end (e.g., a superior end) of the mandibular implant 10.The collar portion 14 may be positioned intermediate of the head portion16 and the stem portion 12 in the superior-inferior direction.

The axis X-X of the stem portion 12 and the collar portion 14 may passthrough the head portion 16. For example, the head portion 16 may besubstantially centered on the collar portion 14 and/or stem portion 12(e.g., substantially centered on the axis X-X). Stated differently, thestem portion 12, the collar portion 14, and the head portion 16 may besubstantially aligned along the axis X-X. In some embodiments, the headportion 16 may be cylindrical such that the head portion 16 is formedabout or defines axis X2-X2, as shown in FIGS. 1, 3, 4 and 7. In somesuch embodiments, the axis X-X of the stem portion 12 and the collarportion 14 may be substantially perpendicular to the axis X2-X2 of thehead portion 16. The exterior surface 32 of the head portion 16 may becircular or elliptical in shape in the sagittal plane (e.g., extendabout the axis X2-X2). In some embodiments, the head portion 16 may bekidney-shaped or otherwise configured to allow for, or provide,multi-plane range of motion with or against a fossa or fossa component,as described further below.

As shown in FIGS. 1-11, the head portion 16 may be elongated or extendedin the medial-lateral direction. For example, the head portion 16 mayinclude or define lateral ends or sides 34 in the medial-lateraldirection (e.g., along the axis X-X). The lateral ends 34 of the headportion 16 in the medial-lateral direction may be arcuate or curved toform rounded or blunt ends of the head portion 16. The head portion 16may define or include a width W3 in the medial-lateral direction betweenthe lateral sides 34 (e.g., along the axis X2-X2), as shown in FIGS. 3and 7. In some embodiments, the width W3 of the head portion 16 may bewithin the range of about 10 mm to about 15 mm, or within the range ofabout 11 mm to about 12 mm.

As also shown in FIGS. 1-11, at least a medial portion of the exteriorsurface 32 of the head portion 16 may arcuate or curved in the sagittalplane (e.g., arcuate about the axis X2-X2 extending in themedial-lateral direction). While arcuate in the sagittal plane, thearcuate exterior surface 32 may be elongated or extend linearly in themedial-lateral direction (at least in a medial portion of the headportion 16) between the lateral ends 34. In some embodiments, thearcuate exterior surface 32 may extend parallel to the axis X2-X2. Inthis way, the cylindrical (i.e., elongate and arcuate) exterior surface32 of the head portion 16 may provide a stable rotational joint surfacefor rotation and/or translation with a fossa or fossa component (asexplained further below).

As shown in FIG. 4, the head portion 16 may define a depth D1 in theposterior-anterior direction (e.g., along the axis X2-X2). In theexemplary illustrated embodiment shown in FIGS. 1-11, as the exteriorsurface 32 of the head portion 16 is cylindrical, the arcuate exteriorsurface 32 may defined by a radius (extending from the axis X2-X2) thatis equal to one half of the depth D1 of the head portion 16. In someembodiments, the depth D1 of the head portion (or, potentially, twicethe radius defining the exterior surface 32) may be sized or otherwiseconfigured to provide anatomically correct positioning, rotation,articulation and/or movement of the implant 10 with respect to atemporal bone when the head portion 16 is in abutment with a fossa or afossa component 44, as shown in FIG. 11.

In use, as shown in FIGS. 8-11, the mandibular implant 10 may beimplanted into a condyle 40 of a mandible 42 to form the mandibleportion of a temporomandibular joint. Specifically, as shown in FIG. 9,the stem portion 12 of the mandibular implant 10 is inserted into anintramedullary canal of a condyle 40 of the mandible 42. The condyle 40may be drilled or otherwise prepared for the acceptance of the stemportion 12 within the intramedullary canal. For example, the condyle 40may be drilled or otherwise hollowed out to form an aperture or cavitythat is substantially similar in size and/or shape to the stem portion12 of the implant 10, as shown in FIG. 9.

The mandibular implant 10 may be aligned with the aperture in thecondyle 40 and implanted in the condyle 40 such that the implant 10generally extends in the superior-inferior direction from the headportion 16 to the inferior end 18 of the stem portion 12, as shown inFIGS. 8-11 (the aperture or cavity in the condyle 40 may likewise beprepared). In some embodiments, the stem portion 12 of the implant 10may be implanted in a condyle 40 (and/or the condyle 40 likewiseprepared) such that the implant 10 is angled in theanterior-to-posterior direction as is extends into the condyle 42 (i.e.,as it extends in the superior-to-inferior direction), as show in FIGS.8, 9 and 11. For example, the axis X-X of the implant 10 may be angledin the anterior-posterior direction (i.e., angled with respect to thefrontal plane). As shown in FIG. 10, the stem portion 12 of the implant10 may be implanted in a condyle 40 (and/or the condyle 40 likewiseprepared) such that the implant 10 is substantially parallel to thesagittal plane, as shown in FIG. 10. In some alternative embodiments,the axis X-X of the implant 10 may be angled in the medial-lateraldirection (i.e., angled with respect to the sagittal plane). Forexample, in some such alternative embodiments the stem portion 12 of theimplant 10 may be implanted in a condyle 40 (and/or the condyle 40likewise prepared) such that the implant 10 is angled in thelateral-to-medial direction as is extends into the condyle 42 (i.e., asit extends in the superior-to-inferior direction). The implant 10 may beoriented such that the arcuate exterior surface 32 may be extended inthe medial-lateral direction (i.e., the width W3 of the head portion 16along the axis X2-X2 extends or is elongated in the medial-lateraldirection).

As shown in FIGS. 8-11, the stem portion 12 of the implant 10 may beinserted within the condyle 40 generally in an superior-to-inferiordirection until the end portion of the condyle 40 (extending about thestem portion 12) is seated within the channel 22 (i.e., positionedbetween the collar portion 14 and the stem portion 12), as illustratedin FIG. 9. The superior end of the condyle 40 may abut the superior edgeor end 27 of the channel 22. In some embodiments, the superior tipportion of the condyle 40 may be resected before the implant 10 isimplanted. For example, the superior tip of the condyle 40 may be shapedor formed to match the shape and/or orientation of the superior edge orend 27 of the channel 22. The superior tip portion of the condyle 40 maybe resected to accommodate the length of the implant 10 extending abovethe condyle 40 to ensure the mandible is in its anatomically correctposition with respect to the temporal bone when the head portion 16 isin abutment with the fossa or a fossa component 44, as shown in FIG. 11.

As shown in FIG. 11, after implantation of the implant (and,potentially, a fossa component 44) the arcuate surface 32 of the headportion 16 of the intramedullary implant 10 may abut and articulate withan arcuate surface of the fossa or a fossa component 44 of the temporalbone 46 after implantation. The arcuate surface of the fossa or a fossacomponent 44 may be defined by a radius that is greater than a radiusdefining the arcuate exterior surface 32 of the head portion 16. Duringuse, the arcuate exterior surface 32 of the head portion 16 of theimplant 10 is able to articulate or rotate on the arcuate surface of thefossa component 44. In this way, the implant 10 may provide areconstructed temporomandibular joint with a range of motionsubstantially similar to normal anatomical parameters. Afterimplantation, the intramedullary implant 10 may act to absorb and/ordistribute stresses acting on the implant 10. For example, theintramedullary nature of the stem portion 12 of the implant, and/or theferrule effect produced by the collar portion 14 of the implant 10, mayact to distribute the stress acting on the implant 10 and condyle 40 toprevent stress concentrations (typical modes of failure) on the implant10 and condyle 40. Further, the ferrule effect produced by the collarportion 14 of the implant may prevent the condyle 40 from splitting orsplintering during installation of the implant 10 and use of the implant10 with the fossa or a fossa component 44.

It is to be understood that the above description is intended to beillustrative, and not restrictive. Numerous changes and modificationsmay be made herein by one of ordinary skill in the art without departingfrom the general spirit and scope of the invention as defined by thefollowing claims and the equivalents thereof. For example, theabove-described embodiments (and/or aspects thereof) may be used incombination with each other. In addition, many modifications may be madeto adapt a particular situation or material to the teachings of thevarious embodiments without departing from their scope. While thedimensions and types of materials described herein are intended todefine the parameters of the various embodiments, they are by no meanslimiting and are merely exemplary. Many other embodiments will beapparent to those of skill in the art upon reviewing the abovedescription. The scope of the various embodiments should, therefore, bedetermined with reference to the appended claims, along with the fullscope of equivalents to which such claims are entitled. In the appendedclaims, the terms “including” and “in which” are used as theplain-English equivalents of the respective terms “comprising” and“wherein.” Moreover, in the following claims, the terms “first,”“second,” and “third,” etc. are used merely as labels, and are notintended to impose numerical requirements on their objects. Also, theterm “operably” in conjunction with terms such as coupled, connected,joined, sealed or the like is used herein to refer to both connectionsresulting from separate, distinct components being directly orindirectly coupled and components being integrally formed (i.e.,one-piece, integral or monolithic). Further, the limitations of thefollowing claims are not written in means-plus-function format and arenot intended to be interpreted based on 35 U.S.C. §112, sixth paragraph,unless and until such claim limitations expressly use the phrase “meansfor” followed by a statement of function void of further structure. Itis to be understood that not necessarily all such objects or advantagesdescribed above may be achieved in accordance with any particularembodiment. Thus, for example, those skilled in the art will recognizethat the systems and techniques described herein may be embodied orcarried out in a manner that achieves or optimizes one advantage orgroup of advantages as taught herein without necessarily achieving otherobjects or advantages as may be taught or suggested herein.

While the invention has been described in detail in connection with onlya limited number of embodiments, it should be readily understood thatthe invention is not limited to such disclosed embodiments. Rather, theinvention can be modified to incorporate any number of variations,alterations, substitutions or equivalent arrangements not heretoforedescribed, but which are commensurate with the spirit and scope of theinvention. Additionally, while various embodiments of the invention havebeen described, it is to be understood that aspects of the disclosuremay include only some of the described embodiments. Accordingly, theinvention is not to be seen as limited by the foregoing description, butis only limited by the scope of the appended claims.

This written description uses examples to disclose the invention,including the best mode, and also to enable any person skilled in theart to practice the invention, including making and using any devices orsystems and performing any incorporated methods. The patentable scope ofthe invention is defined by the claims, and may include other examplesthat occur to those skilled in the art. Such other examples are intendedto be within the scope of the claims if they have structural elementsthat do not differ from the literal language of the claims, or if theyinclude equivalent structural elements with insubstantial differencesfrom the literal language of the claims.

We claim:
 1. A mandibular implant, comprising: an intramedullary stemportion; a collar portion extending substantially about the stemportion, the collar portion forming a channel extending between thecollar portion and the stem portion about the stem portion; and a headportion including an arcuate external surface, wherein the collarportion is intermediate the stem portion and the head portion, andwherein the stem portion, the collar portion and the head portion aresubstantially aligned.
 2. The mandibular implant of claim 1, wherein thestem portion, the collar portion and the head portion are integral toeach other.
 3. The mandibular implant of claim 1, wherein the stemportion is configured to be implanted within a condyle of a mandible. 4.The mandibular implant of claim 1, wherein the stem portion defines afree end and is elongate between the inferior end and a superior endportion.
 5. The mandibular implant of claim 4, wherein the collarportion extends from the superior end portion of the stem portion. 6.The mandibular implant of claim 1, wherein the collar portion includes afirst portion with an outer surface that tapers outwardly as it extendsin a first direction from the head portion towards the stem portion. 7.The mandibular implant of claim 6, wherein the collar portion includes asecond portion that extends from the first portion along the firstdirection and about the stem portion.
 8. The mandibular implant of claim7, wherein at least the second portion of the collar portion forms thechannel.
 9. The mandibular implant of claim 7, wherein the secondportion of the collar portion is ring-shaped, and wherein the stemportion is cylindrical.
 10. The mandibular implant of claim 1, whereinthe stem portion defines a first axis and the collar portion defines asecond axis, and wherein the first axis and the second axis are aligned.11. The mandibular implant of claim 10, wherein the head portion definesa third axis that is oriented substantially perpendicular to the firstaxis and the second axis, and wherein the head portion extends along thedirection of the third axis.
 12. The mandibular implant of claim 11,wherein the arcuate external surface of the head portion extends aboutthe third axis.
 13. The mandibular implant of claim 11, wherein thearcuate external surface of the head portion extends linearly along thedirection of the third axis.
 14. The mandibular implant of claim 1,wherein the stem portion and the collar portion define a first axis andthe head portion defines a third axis oriented substantiallyperpendicular to the first axis, and wherein the stem portion defines afirst width extending along the direction of the third axis within therange of about 2 mm to about 9 mm, the channel defines a second widthextending along the direction of the third axis and about the stemportion of about 2 mm, and the head portion defines a third widthextending along the direction of the third axis within the range ofabout 10 mm to about 15 mm.
 15. The mandibular implant of claim 1,wherein the channel defines a width extending between an outer surfaceof the stem portion and an inner surface of the collar portion of about2 mm and a length extending substantially perpendicular to the width ofabout 4 mm.
 16. A system for replacing a temporomandibular joint,comprising: a biocompatible fossa component configured to be fixed to atemporal bone; and a biocompatible mandibular component configured to befixed to a mandible bone comprising: an intramedullary stem portion; acollar portion extending substantially about the stem portion, thecollar portion forming a channel between the collar portion and the stemportion; and a head portion including a first arcuate external surface,wherein the collar portion is intermediate the stem portion and the headportion.
 17. The system of claim 16, wherein the biocompatible fossaincludes a second arcuate surface configured to abut and articulate withthe first arcuate external surface of the head portion.
 18. The systemof claim 17, wherein the first arcuate external surface of the headportion is defined by a first radius, and the second arcuate surface ofthe biocompatible fossa is defined by a second radius that is greaterthan the first radius.
 19. The system of claim 16, wherein the stemportion, the collar portion and the head portion are of one-piececonstruction.
 20. The system of claim 16, wherein the collar portionincludes a first portion with a outer surface that tapers outwardly asit extends in a first direction from the head portion towards the stemportion.
 21. The system of claim 20, wherein the collar portion includesa second portion that extends from the first portion along the firstdirection and about the stem portion.
 22. The system of claim 21,wherein at least the second portion of the collar portion forms thechannel about the stem portion.
 23. The system of claim 16, wherein thestem portion defines a first axis and the collar portion defines asecond axis aligned with the first axis, wherein the head portiondefines a third axis that is oriented substantially perpendicular to thefirst axis and the second axis, and wherein the head portion iselongated along the direction of the third axis.
 24. The system of claim23, wherein the arcuate external surface of the head portion extends atleast partially about the third axis and extends linearly along thedirection of the third axis for a first width.
 25. A method of treatinga temporomandibular joint, comprising; forming an aperture in a condyleof a mandible; aligning a stem portion of a mandibular implant with theaperture in the condyle, implanting the mandibular implant into theaperture of the condyle such that an end portion of the condyleextending about the stem portion is positioned within a channel of themandibular implant formed between the stem portion and a collar portionof the implant, and a head portion of the implant including an arcuateexternal surface is positioned superior to the condyle for articulationwith a fossa or fossa component.
 26. The method of claim 25, wherein thecollar portion of the implant forms a ferrule effect to the end portionof the condyle.
 27. The method of claim 25, further comprising resectinga superior tip portion of the condyle of the mandible.
 28. The method ofclaim 25, further comprising implanting the mandibular implant into theaperture of the condyle such that the implant is angled in theanterior-to-posterior direction as it extends into the condyle in thesuperior-to-inferior direction.
 29. The method of claim 28, furthercomprising implanting the mandibular implant into the aperture of thecondyle such that the implant is substantially parallel to the sagittalplane.
 30. The method of claim 28, further comprising implanting themandibular implant into the aperture of the condyle such that theimplant is angled in the lateral-to-medial direction as is extends intothe condyle in the superior-to-inferior direction.
 31. The method ofclaim 25, further comprising implanting a fossa component in a temporalbone corresponding to the condyle of the mandible.
 32. The method ofclaim 25, wherein the arcuate external surface of the head portion ofthe implant is elongated and extends linearly along a first width, andfurther comprising orienting the implant such that the first width ofthe head portion extends in the medial-lateral direction.